Anything related to Park tickets can be done at any of the following locations:
Any Park (including Water Parks) ticket booth. This includes the TTC.
Any Guest Relations Office (GRO) outside the parks. This includes the Water Parks, TTC and DTD.
Any GRO inside the Parks.
Guest Services/Concierge in the Resorts; however they cannot do anything related to Annual Passes.
This includes "will-call", upgrading any tickets, replacing any tickets, converting an AP voucher to an AP, or selling an AP.
Anything that can be done related to tickets at a GRO can also be done at a regular ticket window. The ticket windows cannot do things such as make reservations, unscramble problems related to room keys, or handle Lost and Found or Guest Recovery.